A typical two-pole circuit breaker (for example, a residential two-pole circuit breaker) receives as inputs two line voltages and a neutral voltage. The two line voltages (line-to-neutral voltages) typically are 120V alternating current (“AC”) signals, 180 degrees out of phase from one another. Each line voltage alternates in polarity with respect to the neutral voltage, which is determined from the two line voltages in a conventional manner. The sum of the two line voltages (the line-to-line voltage) is a 240V AC voltage.
A microprocessor or controller in the circuit breaker can be used to measure line voltages. For example, circuits can be used to divide a line voltage and output the divided signal to the microprocessor. The microprocessor includes an analog to digital (A/D) converter to receive the analog voltage and convert it to a digital voltage for measurement by the microprocessor. Microprocessors often have multiple analog inputs connected, through a multiplexer, to the A/D converter. However, the number of analog inputs is limited.
Circuit breakers generally monitor either the line-to-line voltage or the line-to neutral voltages. For a two-pole circuit breaker, measuring each of the line-to-neutral voltages would require the use of two analog inputs of the microprocessor and circuit components on the printed circuit board assembly (PCBA) for measuring each line to neutral voltage. Measuring the line-to-line voltage would also require the use of an analog input and additional circuit components on the PCBA. Thus, a total of at least three analog inputs are required to measure each of the three voltage combinations. This adds complexity, increases processing times, and consumes an additional analog input.
What is needed is a way to measure the individual line voltages, as well as the combined 240V AC signal, using fewer analog inputs and fewer circuit components. Aspects and embodiments disclosed herein are directed to addressing/solving these and other needs.